Expression of genetic information during gernation of bacterial spores. The dormant spores of B. cereus carry an RNA-P whose core (beta, beta, alpha 2) has the immunological properties and electrophoretic mobility of the vegetative enzyme. The RNA-P carried by the dormant spore ought to be stable in vivo through germination and outgrowth, because the enzyme is not synthesized de novo in any considerable amount until the end of outgrowth. However, the beta' chain extracted from dormant spores is unstable to incubation and purification, while the beta chain and the other proteins are stable. This instability is probably due to a proteolytic attack. The preferential attack of the sporal beta' was also observed by other authors (14) and is rather puzzling. Possibly the other sporal proteins are protected from proteolysis by binding to sporal components. The responsible proteolytic enzyme is probably the one we found attached to the surface of the dormant spores. This enzyme is destroyed by the heat treatment (90 min. at 65 degrees C) of "spore activation". This finding could explain why the RNA-P extracted from activated and germinated spores is stable. The real function of the proteolytic enzyme may be to provide the spore with the germinating factors from the natural environment. While it should be excluded that the RNA-P "core" controls, directly, the synthesis of the few "early" proteins at germination or the shift to many syntheses at outgrowth in rich medium, (15,16), this can occur by complexing the "core" with sporal components or with specific o-like peptides.